JP2012119794A - Electronic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress characteristic variations due to length errors in distributed constant lines or due to manufacturing variations.SOLUTION: An electronic circuit includes: a first transistor T1 having a control terminal, a first terminal and a second terminal; a second transistor T2 having a control terminal connected with the second terminal of the first transistor, and a second terminal connected with a DC power supply; a plurality of DC paths 11, 12 comprising independent wiring for supplying DC currents from the first terminal of the second transistor to the second terminal of the first transistor; and distributed constant lines L11, L12 disposed in series within the plurality of DC paths, respectively.

Description

  The present invention relates to an electronic circuit, for example, a current reuse amplifier circuit.

  In a multi-stage amplifier circuit, a current reuse amplifier circuit that uses a subsequent DC (direct current) current as a previous DC current is also known (for example, Non-Patent Document 1). A current reuse amplifying circuit provided with a stub and a capacitor for widening in the millimeter wave band or the like is known (for example, Non-Patent Document 2).

2000 IEEE MTT-S Dig., Vol. 1, pp17-20 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS VOL. 15, NO. 5, (2005)

  The amplifier circuit of Non-Patent Document 2 can have a wider bandwidth than the amplifier circuit of Non-Patent Document 1. However, at high frequencies such as millimeter waves, the distributed constant line becomes short, and characteristic fluctuations increase due to errors in the length of the distributed constant line or manufacturing variations.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress fluctuations in characteristics due to errors in the length of distributed constant lines or manufacturing variations.

  In the present invention, a first transistor having a control terminal, a first terminal, and a second terminal, a second terminal of the first transistor connected to the control terminal, and a DC power source connected to the second terminal A second transistor, a plurality of DC paths composed of mutually independent wirings for supplying a DC current from the first terminal of the second transistor to the second terminal of the first transistor, and a plurality of DC paths in series in the plurality of DC paths, respectively. An electronic circuit comprising: a distributed constant line provided in the electronic circuit. According to the present invention, it is possible to suppress the characteristic variation due to the error in the length of the distributed constant line or the manufacturing variation.

  The said structure WHEREIN: It can be set as the structure which comprises the 1st resistance each provided in series with the said distributed constant line in these DC path | routes. According to this configuration, the potential of the control terminal of the second transistor can be determined.

  In the above configuration, a plurality of the second transistors are provided in parallel, and each of the first terminals of the plurality of second transistors is one of the plurality of DC paths between the second terminals of the first transistors. It can be set as the structure connected through one.

  In the above configuration, a plurality of the first transistors may be provided in parallel.

  In the above configuration, a plurality of the first transistors may be provided, and first terminals of the plurality of first transistors may be grounded via a second resistor. According to this structure, heat dissipation can be improved.

  In the above configuration, each of the first resistors is provided between the distributed constant line and the first terminal of the second transistor, and a plurality of the first resistors are provided between the first resistor and the plurality of distributed constant lines. The connection point can be grounded via a capacitor. According to this configuration, a broadband electronic circuit can be provided.

  The said structure WHEREIN: The reactance component of the said distributed constant line provided in the said several DC path | route can be set as the same structure.

  The said structure WHEREIN: The resistance value of the said 1st resistance provided in each of these DC path | routes can be set as the same structure.

  According to the present invention, it is possible to suppress characteristic fluctuations due to an error in the length of distributed constant lines or manufacturing variations.

FIG. 1 is a circuit diagram of an amplifier circuit according to a comparative example. FIG. 2 is a circuit diagram of an amplifier circuit according to the first embodiment. FIG. 3 is a circuit diagram of an amplifier circuit according to the second embodiment. FIG. 4 is a circuit diagram of an amplifier circuit according to the third embodiment. FIG. 5 is a schematic plan view when the amplifier circuit according to the third embodiment is formed as an MMIC on a semiconductor substrate. FIG. 6A is a diagram illustrating S21 with respect to the frequency of the amplifier circuit according to the third embodiment, and FIG. 6B is a diagram illustrating S11 and S22 with respect to the frequency.

  First, a current reuse amplifier circuit will be described using a comparative example. FIG. 1 is a circuit diagram of an amplifier circuit according to a comparative example. Referring to FIG. 1, the amplifier circuit 102 is a two-stage amplifier circuit having a first transistor T1 and a second transistor T2. The case where FETs (Field Effect Transistors) are used as the first transistor T1 and the second transistor T2 will be described as an example.

  A capacitor C7 and distributed constant lines L10 and L9 are connected in series between the input terminal Tin of the amplifier circuit 102 and the gate G1 (control terminal) of the first transistor T1. A node between the distributed constant lines L10 and L9 is grounded via the distributed constant line L8 and the capacitor C6. A resistor R3 is connected in parallel to the capacitor C6. The capacitor C7 is a DC cut capacitor. The distributed constant lines L8, L9 and L10 and the capacitor C6 match the impedance of the input terminal Tin with the input impedance of the first transistor T1. The resistor R3 determines the potential of the gate G1.

  The source S1 (first terminal) of the first transistor T1 is grounded via the capacitor C5 and the resistor R2. The capacitor C5 and the resistor R2 are connected in parallel. The capacitor C5 grounds the source S1 in a high frequency manner. The resistor R2 grounds the source S1 in a DC manner. Further, the potential of the source S1 is determined. As a result, the source S1 is grounded in a direct current and high frequency manner. The drain D1 (second terminal) of the first transistor T1 is connected to the gate G2 (control terminal) of the second transistor T2 via the signal path 20. The signal path 20 includes distributed constant lines L2 and L3 connected in series.

  The source S2 (first terminal) of the second transistor T2 is grounded via the capacitor C1 (first capacitor). A node N1 between the distributed constant line L2 and the distributed constant line L3 is connected to a node N2 between the source S2 of the second transistor T2 and the capacitor C1 via the resistor R1 and the distributed constant line L1 in series. . The distributed constant lines L1, L2, and L3 match the impedance between the first transistor T1 and the second transistor T2. The resistor R1 provides a potential difference between the source S2 and the gate G2, and determines the potential applied to the gate G2. Further, the resistor R1 functions in a resistance matching manner when matching the impedance between the first transistor T1 and the second transistor T2.

  Distributed constant lines L7 and L6 and a capacitor C4 are connected in series between the drain D2 (second terminal) of the second transistor T2 and the output terminal Tout. A node between the distributed constant lines L7 and L6 is grounded via the distributed constant line L5 and the capacitor C3. A DC power source Vd is connected to the capacitor C3 in parallel. Thereby, the DC power source Vd is connected to the drain D2, and a DC voltage is applied. The distributed constant lines L5, L6 and L7, and the capacitor C3 match the output impedance of the second transistor T2 and the impedance of the output terminal Tout. Capacitors C3 and C4 are DC cut capacitors.

  A signal (for example, a high frequency signal) input from the input terminal Tin is input to the gate G1 of the first transistor T1. The first transistor T1 amplifies the signal input to the gate G1 and outputs it from the drain D1. The output signal passes through the signal path 20 and is input to the gate G2 of the second transistor T2. The second transistor T2 amplifies the signal input to the gate G2, and outputs it from the drain D2. The amplified signal is output from the output terminal Tout.

  Due to the capacitor C1, the source S2 of the second transistor T2 is not grounded in terms of DC. For this reason, the direct current supplied from the DC power source Vd is distributed in the distributed constant lines L5 and L7, the second transistor T2, the node N2, the distributed constant line L1, the resistor R1, the node N1, and the distribution as indicated by the broken arrows in FIG. The current flows to the ground via the constant line L2, the first transistor T1, and the resistor R2. A path through which a direct current flows at this time is defined as a direct current path. Thereby, the voltage of the DC power supply Vd is applied in series to the first transistor T1 and the second transistor T2, and the direct current supplied from the DC power supply Vd flows through the first transistor T1 and the second transistor T2. As a result, current consumption can be reduced as compared with an amplifier circuit in which a current is independently supplied to each stage transistor. The resistor R1 has a function of providing a potential difference between the source S2 and the gate G2 of the second transistor T2.

  However, when the frequency of the signal to be amplified increases, for example, in the case of millimeter waves, the distributed constant line used for the DC path is shortened. Therefore, in the case of a single DC path configuration as in the comparative example, the distributed constant line is shortened, the length of the distributed constant line is likely to vary due to errors or manufacturing variations, and the characteristics of the distributed constant line are likely to vary. Become. Hereinafter, an embodiment that solves such a problem will be described.

  FIG. 2 is a circuit diagram of an amplifier circuit according to the first embodiment. As shown in FIG. 2, in the amplifier circuit 100, a DC path 10 (not shown) is divided in parallel into DC paths 11 and 12 between a node N1 and a node N2. In the DC path 11, a distributed constant line L11 and a resistor R11 are directly provided. In the DC path 12, a distributed constant line L12 and a resistor R12 are directly provided. Other configurations are the same as those of the comparative example shown in FIG.

  According to the first embodiment, the plurality of DC paths 11 and 12 for supplying a DC current from the source S2 of the second transistor T2 to the drain D2 of the first transistor T1 are composed of wirings independent of each other. Thereby, the inductance of the distributed constant lines L11 and L12 provided in the DC paths 11 and 12 can be increased. Therefore, each length of the distributed constant lines L11 and L12 can be made larger than that of the distributed constant line L1 of the comparative example. Therefore, characteristic variations due to errors or manufacturing variations can be reduced. In the first embodiment, an example in which the DC paths 11 and 12 are two has been described. However, three or more DC paths connected in parallel and made of mutually independent wirings may be used.

  A plurality of resistors R11 and R12 (first resistor) are provided in series with the plurality of distributed constant lines L11 and L12 in the plurality of DC paths 11 and 12, respectively. The potential of the gate of the second transistor T2 can be determined by the resistors R11 and R12. According to the first embodiment, by providing a plurality of DC paths, it is possible to increase the inductance of each DC path, and to design a distributed constant line longer than that of a single DC path. As a result, it is possible to suppress the length of the distributed constant line due to errors or manufacturing variations, and variations in characteristics associated therewith.

  In the second embodiment, the first transistor T1 and the second transistor T2 are a plurality of examples. FIG. 3 is a circuit diagram of an amplifier circuit according to the second embodiment. As shown in FIG. 3, in the amplifier circuit 101, a plurality of first transistors T11 and T12 are provided in parallel. A plurality of second transistors T21 and T22 are provided in parallel. The sources S11 and S12 of the first transistors T11 and T12 are connected in common at the node N8. The source S11 of the first transistor T11 is grounded via the capacitor C51 and the resistor R21, and the source S12 of the first transistor T12 is grounded via the capacitor C52 and the resistor R22.

  The gates G11 and G12 of the first transistors T11 and T12 are commonly connected at the node N6. The node N6 is connected to the input terminal Tin via distributed constant lines L9 and L10 and a capacitor C7. The drains D11 and D12 of the first transistors T11 and T12 are commonly connected at the node N4. The node N4 is connected to the gates G21 and G22 of the second transistors T21 and T22 via the signal path 20.

  The sources S21 and S22 of the second transistors T21 and T22 are connected in common at the node N9. The source S21 of the second transistor T21 is grounded via the capacitor C11 (first capacitor), and the source S22 of the second transistor T22 is grounded via the capacitor C12 (first capacitor).

  The gates G21 and G22 of the second transistors T21 and T22 are commonly connected at the node N5. Node N5 is connected to signal path 20. The drains D21 and D22 of the second transistors T21 and T22 are commonly connected at the node N7. The node N7 is connected to the DC power source Vd and the output terminal Tout.

  A node N1 between the distributed constant lines L2 and L3 in the signal path 20 is grounded via the distributed constant line L11 and the capacitor C21. One end of the resistor R11 is connected to a node N31 between the distributed constant line L11 and the capacitor C21, and the other end is connected to a node N21 between the source S21 and the capacitor C11. The node N1 is grounded via the distributed constant line L12 and the capacitor C22. One end of the resistor R12 is connected to a node N32 between the distributed constant line L12 and the capacitor C22, and the other end is connected to a node N22 between the source S22 and the capacitor C12.

  The signal path 20 from the first transistors T11 and T12 to the second transistors T21 and T22 is common. On the other hand, the DC path 10 is divided into two paths from the node N7 to the node N1. One DC path 11 is a path of the node N7, the drain D21 of the second transistor T21, the source S21, the node N9, the node N21, the resistor R11, the node N31, the distributed constant line L11, and the node N1. The other DC path 22 is a path of the node N7, the drain D22 of the second transistor T22, the source S22, the node N22, the resistor R12, the node N32, the distributed constant line L12, and the node N1.

  Further, the DC path 10 is divided into two paths from the node N4 to the ground. One DC path 13 is a path of the node N4, the drain D11, the source S11, the node N8, the resistor R21, and the ground of the first transistor T11. The other DC path 14 is a path of the node N4, the drain D12, the source S12, the resistor R22, and the ground of the first transistor T12.

  According to the second embodiment, each of the sources S21 and S22 of the plurality of second transistors T21 and T22 is connected to the drains of the first transistors T11 and T12 via one of the plurality of DC paths 11 and 12. Connected. For example, the gates G21 and G22 of the plurality of second transistors T21 and T22 are commonly connected at the node N5 (first connection point). The plurality of DC paths 11 and 12 are respectively connected to the sources S21 and S22 of the second transistors T21 and T22 and the node N1 (second connection point: the node N5 and the drains D11 and D12 of the first transistors T11 and T12). Node). As described above, the plurality of second transistors T21 and T22 are provided in parallel, and the DC paths 11 and 12 corresponding to the respective second transistors T21 and T22 are provided. Thereby, as in the first embodiment, variation in characteristics can be reduced.

  Further, the drains D11 and D12 of the plurality of first transistors T11 and T12 are commonly connected at a node N4 (third connection point). The plurality of DC paths 11 and 12 are respectively a source S21 and S22 of the second transistors T21 and T22 and a node N1 (second connection point: a node between the node N4 and the gates G21 and G22 of the second transistors T21 and T22). ) And connected to. As described above, the plurality of first transistors T11 and T12 are provided in parallel, and the DC paths 11 and 12 corresponding to the first transistors T11 and T12 are provided. Thereby, as in the first embodiment, variation in characteristics can be reduced.

  Further, the sources S11 and S12 of the plurality of first transistors T11 and T12 are grounded via resistors R21 and R22 (second resistor), respectively. When the first transistors T11 and T12 generate heat, it is difficult to dissipate heat through the capacitor. On the other hand, for example, a thin film resistor formed on a substrate has good thermal conductivity. Therefore, heat dissipation can be improved by grounding the first transistors T11 and T12 through a plurality of resistors.

  Further, each of the plurality of resistors R11 and R12 is provided between the plurality of distributed constant lines L11 and L12 and the sources S21 and S22 of the second transistors T21 and T22, respectively. A plurality of nodes N31 and N32 (connection points) between the plurality of resistors R11 and R12 and the plurality of distributed constant lines L11 and L12 are grounded via capacitors C21 and C22 (second capacitor), respectively. Yes. Thereby, the impedance between the first transistors T11 and T12 and the second transistors T21 and T22 can be matched using the distributed constant lines L11, L12, L2, and L3 and the capacitors C21 and C22.

  For example, the impedance can be matched so that the amplifier circuit 101 has a wide band. For example, the impedance Z1 of the first transistors T11 and T12 viewed from the node N5 and the impedance Z2 of the second transistors T21 and T22 are most closely matched at the first upper limit of the band of the amplifier circuit 101. As the frequency decreases from the first frequency, the matching between the impedances Z1 and Z2 is gradually shifted. This misalignment is adjusted so as to compensate for the gains of the transistors T11, T12, T21, and T22 that gradually increase as the frequency decreases from the first frequency. Thereby, a broadband amplifier circuit can be realized.

  Further, the impedances of the capacitors C21 and C22 at the lower limit of the band of the amplifier circuit 101 are set to be approximately equal to or larger than the impedances of the resistors R11 and R12. Thereby, the signal of this frequency is grounded via the resistors R11 and R12 in addition to the capacitors C21 and C22. Therefore, the signal via the resistors R11 and R12 is attenuated. Therefore, oscillation at the lower limit of the band of the amplifier circuit 101 can be suppressed.

  Example 3 is an example in which a simulation was performed. FIG. 4 is a circuit diagram of an amplifier circuit according to the third embodiment. As shown in FIG. 4, the amplifier circuit 101a includes a first transistor T1 and a second transistor T2 as compared with FIG. 3 of the second embodiment. The resistor R3 is not provided. The gate G1 of the first transistor T1 is grounded through two paths. In one path, the gate G1 is grounded via a distributed constant line L19 in series and a parallel circuit of a capacitor C81 and a resistor R31 in series. In the other path, the distributed constant line L20 is grounded in series, and a parallel circuit of the capacitor C82 and the resistor R32 is grounded in series. A distributed constant line L17 is connected between the source S1 of the first transistor T1, the capacitor C51, and the resistor R21. A distributed constant line L18 is connected between the source S1 of the first transistor T1, the capacitor C52, and the resistor R22. A distributed constant line L13 is connected between the node N31 and the capacitor C21, and a distributed constant line L14 is connected between the node N32 and the capacitor C22. A distributed constant line L15 is connected between the source S2 of the second transistor T2 and the node N21, and a distributed constant line L16 is connected between the source S2 and the node N22. An internal resistor R4 is connected to the DC power source Vd. Other configurations are the same as those of the second embodiment shown in FIG.

  FIG. 5 is a schematic plan view when the amplifier circuit according to the third embodiment is formed as an MMIC (Monolithic Microwave Integrated Circuit) on the semiconductor substrate 30. The capacitor in FIG. 5 is formed by a MIM (Metal Insulator Metal) capacitor formed on the semiconductor substrate 30. The MIM capacitor includes a lower electrode made of a metal such as an Au film formed on the semiconductor substrate 30 or through an insulating film, a dielectric film such as a silicon nitride film formed on the lower electrode, and a dielectric And an upper electrode made of a metal such as an Au film formed on the film. The resistor is composed of a thin film resistor formed on the semiconductor substrate 30 or on the semiconductor substrate via an insulating film. The distributed constant line is composed of a metal film such as Au formed on the semiconductor substrate 30 or on the semiconductor substrate via an insulating film, and is formed of, for example, a microstrip line.

  The first transistor T1 and the second transistor T2 are provided in the semiconductor substrate 30, respectively. The first transistor T1 has an active region 31. In the active region 31, a source S11, a gate G11, a drain D1, a gate G12, and a source S12 are sequentially arranged. The first transistor T1 is a multi-finger FET and two first transistors T11 and T12 having a common drain D1. The second transistor T2 has an active region 32. In the active region 32, a source S21, a gate G21, a drain D2, a gate G22, and a source S22 are sequentially arranged. The second transistor T2 is a multi-finger FET and two second transistors T21 and T22 having a common drain D2.

Table 1 is a table showing values used for the simulation in the amplifier circuit according to the third embodiment. In Table 1, the distributed constant line has a width (10 μm), an effective dielectric constant of 1.5, a characteristic impedance of 50Ω, and a length (unit: μm). The unit of the capacitor is pF, the unit of resistance is Ω, and the unit of power supply voltage is V. As the first transistors T11 and T12 and the second transistors T21 and T22, simulation was performed using a GaAs / AlGaAs HEMT (High Electron Mobility Transistor). The gate widths of the first transistors T11 and T12 and the second transistors T21 and T22 were 80 μm and 40 μm × 2. That is, each of the first transistors T11 and T12 and the second transistors T21 and T22 is formed by two fingers each having a width of 40 μm.

  FIG. 6A is a diagram illustrating S21 with respect to the frequency of the amplifier circuit according to the third embodiment, and FIG. 6B is a diagram illustrating S11 and S22 with respect to the frequency. As shown in FIG. 6A, the gain is substantially constant at about 60 to 96 GHz, and a gain of about 8 dB is obtained. In addition, S11 and S22 are suppressed to −10 dB or less in this frequency range. By providing a plurality of independent DC paths 11 and 12 as in the third embodiment, the DC paths 11 and 12 become more distributed constant paths. As a result, the bandwidth of the amplifier circuit can be increased.

  The reactance components of the plurality of distributed constant lines L11 and L12 are the same. The resistance values of the plurality of resistors R11 and R12 are the same. As a result, the balance between the DC paths 11 and 12 is improved, and a wider band is possible. Furthermore, by making the two-dimensional arrangement of the DC paths 11 and 12 on the substrate 30 symmetrical about the second transistor, it is possible to increase the bandwidth. Furthermore, the reactance components of the distributed constant lines L13 and L14 are the same, and the capacitances of the capacitors C21 and C22 are the same. The reactance components of the distributed constant lines L15 and L16 are the same. Capacitors C11 and C12 have the same capacitance. As a result, the balance in terms of high frequency is improved, and a wider band is possible. Further, the two-dimensional arrangement of the distributed constant line L13, the capacitor C21, the distributed constant line L15, and the capacitor C11 and the distributed constant line L14, capacitor C22, distributed constant line L16, and capacitor C11 is symmetric with respect to the second transistor T2. And As a result, the balance in terms of high frequency is improved, and a wider band is possible.

  Further, the resistance values of the plurality of resistors R21 and R22 are the same. The reactance components of the distributed constant lines L17 and L18 are the same. Capacitors C51 and C52 have the same capacitance. As a result, the balance between the DC paths 13 and 14 is improved, and a wider band is possible. Furthermore, the reactance components of the distributed constant lines L19 and L20 are the same. Capacitors C81 and C82 have the same capacitance. The resistance values of the resistors R31 and R32 are the same. As a result, the balance in terms of high frequency is improved, and a wider band is possible. Further, the two-dimensional arrangement of the distributed constant lines L17 and L19, capacitors C51 and C81, resistors R21 and R31, and distributed constant lines L18 and L20, capacitors C52 and C82, and resistors R22 and R32 are centered on the first transistor T1. To be symmetrical. As a result, the balance in terms of high frequency is improved, and a wider band is possible.

  Furthermore, as shown in FIG. 5, by forming the first transistor T1 and the second transistor T2 symmetrically, the balance of the DC paths 13 and 14 is improved, and a wider band is possible. Further, by using both sides of the first transistor T1 and the second transistor T2 as sources, the DC paths 13 and 14 can be arranged symmetrically, and a wide band can be realized.

  One first transistor may be provided as in the first embodiment, or a plurality of first transistors may be provided as in the second embodiment. Furthermore, one second transistor may be provided as in the first embodiment, or a plurality of second transistors may be provided as in the second embodiment.

  Each of the first transistor and the second transistor may be an FET having a single gate finger. Each of the first transistor and the second transistor may be a multi-finger FET having a plurality of gate fingers.

  In the first and second embodiments, FETs have been described as the first transistor T1 and the second transistor T2. However, the first transistor T1 and the second transistor T2 may be bipolar transistors. In this case, the emitter corresponds to the first terminal, the collector corresponds to the second terminal, and the base corresponds to the control terminal. The distributed constant line may be an inductance element such as a short stub.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

10 to 14 DC path 20 signal path C1 to C82 capacitor L1 to L22 distributed constant line R1 to R4 resistance T1 first transistor T2 second transistor

Claims (8)

A first transistor having a control terminal, a first terminal, and a second terminal;
A second transistor having a control terminal connected to the second terminal of the first transistor and a second terminal connected to a DC power supply;
A plurality of DC paths composed of mutually independent wirings for supplying a DC current from the first terminal of the second transistor to the second terminal of the first transistor;
A distributed constant line provided in series in each of the plurality of DC paths;
An electronic circuit comprising:   The electronic circuit according to claim 1, wherein each of the plurality of direct current paths includes a first resistor provided in series with the distributed constant line. A plurality of the second transistors are provided in parallel;
The first terminals of the plurality of second transistors are connected to the second terminals of the first transistors via one of the plurality of DC paths. The electronic circuit according to 1 or 2.   4. The electronic circuit according to claim 1, wherein a plurality of the first transistors are provided in parallel. 5. A plurality of the first transistors are provided,
5. The electronic circuit according to claim 1, wherein first terminals of the plurality of first transistors are each grounded via a second resistor. 6. Each of the first resistors is provided between the distributed constant line and a first terminal of the second transistor,
The electronic circuit according to claim 2, wherein a plurality of connection points between the first resistor and the plurality of distributed constant lines are grounded via a capacitor.   The electronic circuit according to claim 1, wherein reactance components of the distributed constant lines provided in the plurality of DC paths are the same.   The electronic circuit according to claim 2, wherein resistance values of the first resistors provided in the plurality of DC paths are the same.

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